Pillar-shaped semiconductor device and method for manufacturing the same

ABSTRACT

On a semiconductor base that extends in a band shape in a direction (first direction) perpendicular to a line X-X′ direction (second direction) in plan view, an N+ layer, a P+ layer, and Si pillars that also extend in a band shape in the first direction are formed. Subsequently, a gate insulating layer and gate conductor layers are formed so as to surround the Si pillars. Subsequently, a contact hole whose bottom portion is in contact with the N+ layer and the P+ layer is formed in an insulating layer, and a first conductor W layer is formed at the bottom portion of the contact hole. Subsequently, an insulating layer that has a hole is formed in the contact hole. Subsequently, a second conductor W layer is formed in the line X-X′ direction so as to be connected to the gate conductor layers.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application is a continuation application of PCT/JP2020/040575, filed Oct. 29, 2020, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a pillar-shaped semiconductor device and a method for manufacturing the semiconductor device.

2. Description of the Related Art

In recent years, three-dimensional-structure transistors have been used for large-scale integration (LSI). Of these, surrounding gate transistors (SGTs), which are pillar-shaped semiconductor elements, have attracted attention as semiconductor elements that provide semiconductor devices with high integration. In addition, there is a need for semiconductor devices including SGTs with higher integration and higher performance.

A typical planar MOS transistor has a channel extending in the horizontal direction along the upper surface of a semiconductor substrate. By contrast, an SGT has a channel extending in a direction perpendicular to the upper surface of a semiconductor substrate (see, for example, Japanese Unexamined Patent Application Publication No. 2-188966 and Hiroshi Takato, Kazumasa Sunouchi, Naoko Okabe, Akihiro Nitayama, Katsuhiko Hieda, Fumio Horiguchi, and Fujio Masuoka: IEEE Transaction on Electron Devices, Vol. 38, No. 3, pp. 573-578 (1991)). Thus, SGTs allow for higher densities of semiconductor devices than planar MOS transistors.

FIG. 4 shows a schematic structural view of an N-channel SGT. A Si pillar 100 (silicon semiconductor pillars are hereinafter referred to as “Si pillars”) whose conductivity type is P-type or i-type (intrinsic type) has N⁺ layers 101 a and 101 b (semiconductor regions containing donor impurities in high concentrations are hereinafter referred to as “N⁺ layers”) formed in upper and lower portions of the Si pillar 100, one of the N⁺ layers serving as a source, the other serving as a drain. The portion of the Si pillar 100 between the N⁺ layers 101 a and 101 b, which serve as the source and the drain, forms a channel region 102. A gate insulating layer 103 is formed so as to surround the channel region 102. A gate conductor layer 104 is formed so as to surround the gate insulating layer 103. In the SGT, the N⁺ layers 101 a and 101 b, which serve as the source and the drain, the channel region 102, the gate insulating layer 103, and the gate conductor layer 104 are formed so as to have a pillar shape as a whole. A circuit chip including SGTs can achieve a smaller chip size than a circuit chip including planar MOS transistors.

In the SGT in FIG. 4 , the N⁺ layers 101 a and 101 b, which serve as the source and the drain, and the gate conductor layer 104 are connected to an SGT circuit formed on the same substrate through a source connecting line SL, a drain connecting line DL, and a gate connecting line GL, respectively. In this case, a decrease in coupling capacitance between the source connecting line SL, the drain connecting line DL, and the gate connecting line GL leads to an increase in performance of the circuit including the SGT.

SUMMARY OF THE INVENTION

To form an SGT circuit with higher performance and higher integration, reduction in parasitic capacitance between electrodes of each SGT has been required.

To solve the above problems, a method for manufacturing a pillar-shaped semiconductor device according to the present invention is

-   -   a method for manufacturing a pillar-shaped semiconductor device         that includes     -   a first semiconductor pillar standing in a direction         perpendicular to a substrate,     -   a first impurity region disposed at a bottom portion of the         first semiconductor pillar,     -   a second impurity region disposed at a top portion of the first         semiconductor pillar, one of the first impurity region and the         second impurity region serving as a source, the other serving as         a drain, the first semiconductor pillar between the first         impurity region and the second impurity region serving as a         channel,     -   a first gate insulating layer surrounding the first         semiconductor pillar disposed between the first impurity region         and the second impurity region, and     -   a first gate conductor layer surrounding the first gate         insulating layer, the method including:     -   a step of forming the first impurity region such that the first         impurity region extends in a band shape in a first direction in         plan view;     -   a step of forming the first semiconductor pillar that overlaps         the first impurity region in plan view;     -   a step of forming a semiconductor base that includes the first         semiconductor pillar and the first impurity region and extends         in a band shape in the first direction in plan view such that         the semiconductor base connects to the bottom portion of the         first semiconductor pillar;     -   a step of forming the first gate insulating layer and the first         gate conductor layer such that the first semiconductor pillar is         surrounded;     -   a step of forming a first insulating layer disposed at an outer         peripheral portion of the first gate conductor layer;     -   a step of forming, in the first insulating layer, a contact hole         that overlaps the first impurity region disposed in the         semiconductor base in plan view, has a bottom portion in contact         with the first impurity region, and extends in a band shape in         the first direction;     -   a step of forming, at the bottom portion of the contact hole, a         first conductor layer that is in contact with the first impurity         region and extends in a band shape in the first direction;     -   a step of forming, in the contact hole on the first conductor         layer, a second insulating layer that has a hole or is made of a         low-dielectric-constant material;     -   a step of lowering an upper surface of the second insulating         layer below an upper end of the first gate conductor layer; and     -   a step of forming a second conductor layer that is in contact         with the first gate conductor layer and extends in a band shape         in a second direction perpendicular to the first direction in         plan view.

The method for manufacturing a pillar-shaped semiconductor device according to the present invention further includes:

-   -   a step of forming the first semiconductor pillar using a first         mask material layer as an etching mask;     -   a step of forming a third insulating layer that surrounds the         first semiconductor pillar and has an upper surface located at a         bottom portion of the first mask material layer or the top         portion of the first semiconductor pillar in the direction         perpendicular to the substrate;     -   a step of forming a second mask material layer that is disposed         on the third insulating layer and surrounds the exposed first         mask material layer and the top portion of the first         semiconductor pillar with an equal width in plan view;     -   a step of forming, on the third insulating layer, a third mask         material layer that partially overlaps the second mask material         layer and extends in a band shape in the first direction in plan         view; and     -   a step of forming the semiconductor base by etching the third         insulating layer and the first impurity layer using the first         mask material layer, the second mask material layer, and the         third mask material layer as masks.

Furthermore, in the method for manufacturing a pillar-shaped semiconductor device according to the present invention,

-   -   in the first direction in plan view, the second conductor layer         is formed so as to have a width that is smaller than a longest         line segment among point-to-point distances between         intersections of an outer peripheral line of the first gate         conductor layer and straight lines extending in the first         direction.

Furthermore, in the method for manufacturing a pillar-shaped semiconductor device according to the present invention, in the direction perpendicular to the substrate, the first conductor layer is formed so as to have an upper end that is located below a lower end of the first gate conductor layer.

Furthermore, in the method for manufacturing a pillar-shaped semiconductor device according to the present invention, in the direction perpendicular to the substrate, the hole is formed so as to have an upper end that is located below an upper end of the first gate conductor layer.

The method for manufacturing a pillar-shaped semiconductor device according to the present invention further includes:

-   -   a step of forming a second semiconductor pillar on the         semiconductor base on an opposite side of the first conductor         layer from the first semiconductor pillar in the second         direction in plan view;     -   a step of forming a second gate insulating layer such that the         second gate insulating layer surrounds the second semiconductor         pillar;     -   a step of forming a second gate conductor layer such that the         second gate conductor layer surrounds the second gate insulating         layer; and     -   a step of forming the second conductor layer that extends in the         second direction in plan view and is connected to an upper end         portion of the second gate conductor layer.

The method for manufacturing a pillar-shaped semiconductor device according to the present invention further includes:

-   -   a step of forming a third impurity region that is disposed in         the semiconductor base and is adjacent to the first impurity         region in the first direction in plan view;     -   a step of forming a third semiconductor pillar on the third         impurity region;     -   a step of forming a third gate insulating layer such that the         third gate insulating layer surrounds the third semiconductor         pillar;     -   a step of forming a third gate conductor layer such that the         third gate conductor layer surrounds the third gate insulating         layer;     -   a step of forming the second conductor layer such that the         second conductor layer extends in the first direction and is in         contact with the third impurity region in plan view; and     -   a step of forming a third conductor layer that extends in the         second direction in plan view and connects to upper portions of         the first gate conductor layer and the third gate conductor         layer.

The method for manufacturing a pillar-shaped semiconductor device according to the present invention further includes:

-   -   a step of forming, on the substrate, a first impurity layer on         which the first impurity region is based;     -   a step of forming, on the first impurity layer, a first         semiconductor layer on which the first semiconductor pillar is         partially based; and     -   a step of forming, on the first semiconductor layer, a second         impurity layer on which the first semiconductor pillar is         partially based and which forms at least a part of the second         impurity region.

The method for manufacturing a pillar-shaped semiconductor device according to the present invention further includes a step of forming, on the second impurity region, a third impurity layer having the same polarity as that of the second impurity region or a conductive layer made of an alloy or a metal.

To solve the problems described above, a pillar-shaped semiconductor device according to the present invention includes:

-   -   a first semiconductor pillar standing perpendicularly with         respect to a substrate;     -   a first impurity region connecting to a bottom portion of the         first semiconductor pillar and extending in a band shape in a         first direction;     -   a second impurity region disposed at a top portion of the first         semiconductor pillar;     -   a first gate insulating layer surrounding the first         semiconductor pillar disposed between the first impurity region         and the second impurity region;     -   a first gate conductor layer surrounding the first gate         insulating layer;     -   a semiconductor base connecting to the bottom portion of the         first semiconductor pillar, including the first impurity region,         and extending in a band shape in the first direction in plan         view;     -   a first insulating layer disposed at an outer peripheral portion         of the first gate conductor layer;     -   a first material layer disposed in the first insulating layer,         overlapping the first impurity region disposed in the         semiconductor base in plan view, having a bottom portion in         contact with the first impurity region, and extending in a band         shape in the first direction and also extending in a vertical         direction;     -   a first conductor layer extending in a band shape in the first         direction so as to be in contact with the first impurity region         at a bottom portion of the first material layer;     -   a second insulating layer in which the first material layer on         the first conductor layer has a hole whose upper surface is         located below an upper end of the first gate conductor layer or         which is made of a low-dielectric-constant material; and     -   a second conductor layer connecting to the first gate conductor         layer and extending in a band shape in a second direction         perpendicular to the first direction in plan view, wherein the         first conductor layer and the second conductor layer overlap         each other at an intersection in plan view.

Furthermore, in the pillar-shaped semiconductor device according to the present invention, the second conductor layer connects to the gate conductor layer in a contact manner, and in the first direction in plan view, the second conductor layer is formed so as to have a width that is smaller than a longest line segment among point-to-point distances between intersections of an outer peripheral line of the first gate conductor layer and straight lines extending in the first direction.

Furthermore, in the pillar-shaped semiconductor device according to the present invention, in a direction perpendicular to the substrate, an upper end of the first conductor layer is located below a lower end of the first gate conductor layer.

The pillar-shaped semiconductor device according to the present invention further includes:

-   -   a second semiconductor pillar disposed on the semiconductor base         on an opposite side of the first conductor layer from the first         semiconductor pillar in the second direction in plan view;     -   a second gate insulating layer surrounding the second         semiconductor pillar;     -   a second gate conductor layer surrounding the second gate         insulating layer; and     -   the second conductor layer extending in the second direction in         plan view and connected to an upper end portion of the second         gate conductor layer.

The pillar-shaped semiconductor device according to the present invention further includes:

-   -   a third impurity region disposed in the semiconductor base and         adjacent to the first impurity region in the first direction in         plan view;     -   a third semiconductor pillar disposed on the third impurity         region;     -   a third gate insulating layer surrounding the third         semiconductor pillar; and     -   a third gate conductor layer surrounding the third gate         insulating layer,     -   wherein the first conductor layer extends in the first direction         and is adjacent to the third semiconductor pillar in plan view,         and     -   the pillar-shaped semiconductor device further includes a third         conductor layer extending in the second direction in plan view         and connecting to upper portions of the first gate conductor         layer and the third gate conductor layer.

The pillar-shaped semiconductor device according to the present invention further includes:

-   -   a second insulating layer on the third conductor layer;     -   a first contact hole disposed in the second insulating layer on         the third conductor layer; and     -   the second conductor layer disposed on the second insulating         layer and connecting to the third conductor layer through the         first contact hole.

The pillar-shaped semiconductor device according to the present invention further includes, on the second impurity region, a third impurity layer having the same polarity as that of the second impurity region or a conductive layer made of an alloy or a metal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1AA and 1AB are respectively a plan view and a sectional structural view that illustrate a method for manufacturing an SGT-including pillar-shaped semiconductor device according to a first embodiment.

FIGS. 1BA and 1BB are respectively a plan view and a sectional structural view that illustrate the method for manufacturing an SGT-including pillar-shaped semiconductor device according to the first embodiment.

FIGS. 1CA and 1CB are respectively a plan view and a sectional structural view that illustrate the method for manufacturing an SGT-including pillar-shaped semiconductor device according to the first embodiment.

FIGS. 1DA and 1DB are respectively a plan view and a sectional structural view that illustrate the method for manufacturing an SGT-including pillar-shaped semiconductor device according to the first embodiment.

FIGS. 1EA and 1EB are respectively a plan view and a sectional structural view that illustrate the method for manufacturing an SGT-including pillar-shaped semiconductor device according to the first embodiment.

FIGS. 1FA and 1FB are respectively a plan view and a sectional structural view that illustrate the method for manufacturing an SGT-including pillar-shaped semiconductor device according to the first embodiment.

FIGS. 1GA and 1GB are respectively a plan view and a sectional structural view that illustrate the method for manufacturing an SGT-including pillar-shaped semiconductor device according to the first embodiment.

FIGS. 1HA and 1HB are respectively a plan view and a sectional structural view that illustrate the method for manufacturing an SGT-including pillar-shaped semiconductor device according to the first embodiment.

FIGS. 1IA and 1IB are respectively a plan view and a sectional structural view that illustrate the method for manufacturing an SGT-including pillar-shaped semiconductor device according to the first embodiment.

FIGS. 1JA and 1JB are respectively a plan view and a sectional structural view that illustrate the method for manufacturing an SGT-including pillar-shaped semiconductor device according to the first embodiment.

FIGS. 1KA and 1KB are respectively a plan view and a sectional structural view that illustrate the method for manufacturing an SGT-including pillar-shaped semiconductor device according to the first embodiment.

FIGS. 1LA and 1LB are respectively a plan view and a sectional structural view that illustrate the method for manufacturing an SGT-including pillar-shaped semiconductor device according to the first embodiment.

FIGS. 2A and 2B are respectively a plan view and a sectional structural view that illustrate a method for manufacturing an SGT-including pillar-shaped semiconductor device according to a second embodiment.

FIGS. 3A and 3B are respectively a plan view and a sectional structural view that illustrate a method for manufacturing an SGT-including pillar-shaped semiconductor device according to a third embodiment.

FIG. 4 is a three-dimensional structural view that illustrates a conventional example.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a method for manufacturing a pillar-shaped semiconductor device according to the present invention will be described with reference to the drawings.

First Embodiment

Hereinafter, a method for manufacturing a DRAM circuit according to a first embodiment of the present invention will be described with reference to FIG. 1AA to FIG. 1LB. Among these figures, figures with the suffix A are plan views, and figures with the suffix B are sectional structural views taken along a line X-X′ direction (an example of the “second direction” in the claims, hereinafter the same) in the figures with the suffix A.

As illustrated in FIGS. 1AA and 1AB, an N layer 2 is formed on a P layer substrate 1 (an example of the “substrate” in the claims). Subsequently, an N⁺ layer 3 a and a P⁺ layer 3 b extending in a band shape in a direction (an example of the “first direction” in the claims, hereinafter the same) perpendicular to the line X-X′ direction in plan view are formed on the N layer 2.

Next, as illustrated in FIGS. 1BA and 1BB, a P layer 4 is formed by epitaxial growth. Subsequently, mask material layers 5 a and 5 b (examples of the “first mask material layer” in the claims) that are rectangular in plan view are formed on the P layer 4 so as to overlie the N⁺ layer 3 a and the P⁺ layer 3 b, respectively, in plan view.

Next, as illustrated in FIGS. 1CA and 1CB, the P layer 4 and upper portions of the N⁺ layer 3 a and the P⁺ layer 3 b are etched using the mask material layers 5 a and 5 b as masks, thereby forming a Si pillar 7 a and a Si pillar 7 b (examples of the “semiconductor pillar” in the claims) on the N⁺ layer 3 a and the P⁺ layer 3 b, respectively.

Next, as illustrated in FIGS. 1DA and 1DB, a silicon nitride (SiN) layer 9 (an example of the “third insulating layer” in the claims) is formed at outer peripheries of the Si pillars 7 a and 7 b such that the upper surface of the SiN layer 9 is located at top portions of the Si pillars 7 a and 7 b. Subsequently, silicon oxide (SiO₂) layers 10 a and 10 b (examples of the “second mask material layer” in the claims) surrounding the top portions of the Si pillars 7 a and 7 b and the side surfaces of the mask material layers 5 a and 5 b, respectively, with an equal width in plan view are formed. Subsequently, a mask material layer 11 (an example of the “third mask material layer” in the claims) partially overlapping the mask material layers 5 a and 5 b and the SiO₂ layers 10 a and 10 b and extending in a band shape in a direction perpendicular to the line X-X′ direction in plan view is formed. The SiO₂ layers 10 a and 10 b may be formed in such a manner that the mask material layers 5 a and 5 b are covered with SiO₂ layers (not illustrated), and the SiO₂ layers are then etched by, for example, reactive ion etching (RIE). Thus, the SiO₂ layers 10 a and 10 b are formed around the mask material layers 5 a and 5 b, respectively, with an equal width in plan view. Since the mask material layers 5 a and 5 b are formed in a self-aligned manner with respect to the Si pillars 7 a and 7 b, respectively, the SiO₂ layers 10 a and 10 b are formed in a self-aligned manner with respect to the Si pillars 7 a and 7 b, respectively. The SiN layer 9 may be formed after thin SiO₂ layers (not illustrated) are formed on the side surfaces of the Si pillars 7 a and 7 b.

Next, as illustrated in FIGS. 1EA and 1EB, the SiN layer 9, the N⁺ layer 3 a, the P⁺ layer 3 b, the N layer 2, and the P layer substrate 1 are etched using the mask material layers 5 a and 5 b, the mask material layer 11, and the SiO₂ layers 10 a and 10 b as masks to form a P layer base 12 (an example of the “semiconductor base” in the claims) constituted by an N⁺ layer 3 aa, a P⁺ layer 3 bb, an N layer 2 a, and a P layer substrate 1 a. In plan view, the P layer base 12 is shaped such that the N⁺ layer 3 aa and the P⁺ layer 3 bb extending in a band shape in the direction perpendicular to the line X-X′ direction and outer peripheries of the Si pillars 7 a and 7 b partially protrude beyond the mask material layer 11. Portions of the P layer base 12 located where the outer peripheries of the Si pillars 7 a and 7 b partially protrude are formed using the SiN layer 9 a formed in a self-aligned manner with the Si pillars 7 a and 7 b as an etching mask, and thus are formed in a self-aligned manner with the Si pillars 7 a and 7 b.

Next, as illustrated in FIGS. 1FA and 1FB, the mask material layer 11, the SiO₂ layers 10 a and 10 b, and the SiN layer 9 a are removed. Subsequently, a SiO₂ layer 13 is formed so as to surround the P layer base 12 such that the upper surface of the SiO₂ layer 13 is located above the upper surface of the P layer base 12. Subsequently, a hafnium oxide (HfO₂) layer 14 (an example of the “gate insulating layer” in the claims) serving as a gate insulating layer is formed so as to surround the Si pillars 7 a and 7 b by, for example, atomic layer deposition (ALD). Subsequently, a TiN layer (not illustrated) serving as a gate conductor layer and a SiO₂ layer (not illustrated) are formed so as to cover the HfO₂ layer 14. Subsequently, the TiN layer and the SiO₂ layer are polished by chemical mechanical polishing (CMP) such that the upper surfaces thereof are flush with the upper surfaces of the mask material layers 5 a and 5 b. Subsequently, the SiO₂ layer and the TiN layer are etched by RIE such that the upper surfaces thereof are located at upper portions of the Si pillars 7 a and 7 b, thereby forming a TiN layer 15 and a SiO₂ layer 16. Subsequently, a SiN layer (not illustrated) is formed so as to cover the entire surface. Subsequently, the SiN layer is etched by RIE to form SiN layers 17 a and 17 b respectively surrounding the side surfaces of the mask material layers 5 a and 5 b and the top portions of the Si pillars 7 a and 7 b with an equal width in plan view. Depending on the RIE etching conditions, the width of the SiN layers 17 a and 17 b may be unequal in plan view. The SiN layers 17 a and 17 b are only required to respectively surround the side surfaces of the mask material layers 5 a and 5 b and the top portions of the Si pillars 7 a and 7 b.

Next, as illustrated in FIGS. 1GA and 1GB, the SiO₂ layer 16 is removed. Subsequently, the TiN layer 15 is etched by RIE using the SiN layers 17 a and 17 b as masks to form TiN layers 15 a and 15 b (examples of the “gate conductor layer” in the claims) serving as gate conductor layers. In this case, since the SiN layers 17 a and 17 b serving as etching masks are formed in a self-aligned manner with respect to the Si pillars 7 a and 7 b, respectively, the TiN layers 15 a and 15 b are also formed in a self-aligned manner with respect to the Si pillars 7 a and 7 b, respectively.

Next, as illustrated in FIGS. 1HA and 1HB, a SiO₂ layer (not illustrated) is formed so as to cover the entire surface and polished by CMP such that the upper surface thereof is flush with the upper surfaces of the mask material layers 5 a and 5 b, thereby forming a SiO₂ layer 20. Subsequently, a contact hole 21 (an example of the “contact hole” in the claims) partially overlapping the N⁺ layer 3 aa and the P⁺ layer 3 bb, extending in a band shape in the direction perpendicular to the line X-X′ direction in plan view, and having a bottom overlapping the N⁺ layer 3 aa and the P⁺ layer 3 bb is formed. Subsequently, a tungsten (W) layer (not illustrated) is deposited over the entire surface and then polished by CMP such that the upper surface thereof is flush with the upper surfaces of the mask material layers 5 a and 5 b. Subsequently, the W layer in the contact hole 21 is etched by RIE to form a W layer 22 (an example of the “first conductor layer” in the claims) in contact with the N⁺ layer 3 aa and the P⁺ layer 3 bb at a bottom portion of the contact hole 21. The upper surface of the W layer 22 is located below the lower ends of the TiN layers 15 a and 15 b. Before the W layer 22 is formed, a buffer metal layer such as a TaN layer for reducing the contact resistance between the W layer 22 and the N⁺ layer 2 aa and between the W layer 22 and the P⁺ layer 3 bb may be formed.

Next, as illustrated in FIGS. 1IA and 1IB, a SiO₂ layer 24 (an example of the “second insulating layer” in the claims) having a hole 25 therein is formed in the contact hole 21. The upper end of the hole 25 is located below the upper ends of the TiN layers 15 a and 15 b. The SiO₂ layer 24 may be formed of a low-dielectric-constant material such as silicon oxycarbide (SiOC). In this case, the hole 25 may be, but need not be, formed.

Next, as illustrated in FIGS. 1JA and 1JB, the SiO₂ layers 20 and 24 are etched by RIE such that the upper surfaces thereof are located below the upper ends of the TiN layers 15 a and 15 b to form a SiO₂ layer 20 a (an example of the “first insulating layer” in the claims) and a SiO₂ layer 24 a. Subsequently, a W layer (not illustrated) connected to the TiN layers 15 a and 15 b is formed at outer peripheral portions of the TiN layers 15 a and 15 b. Subsequently, a mask material layer 27 partially overlapping the TiN layers 15 a and 15 b and extending in a band shape in the line X-X′ direction in plan view is formed. Subsequently, the W layer is etched using the mask material layer 27 as a mask. Thus, a W layer 26 (an example of the “second conductor layer” in the claims) connected to the TiN layers 15 a and 15 b and extending in the line X-X′ direction in plan view is formed. The width of the W layer 26 in the direction perpendicular to the line X-X′ direction in plan view is smaller than the lengths of the Si pillars 7 a and 7 b in the direction perpendicular to the line X-X′ direction. Subsequently, the mask material layer 27 is removed.

As illustrated in FIGS. 1KA and 1KB, a width L1 of the W layer 26 in the direction perpendicular to the line X-X′ direction is smaller than a width L2 of the outermost peripheries of the TiN layers 15 a and 15 b serving as gates. In plan view, the shape of both ends of the Si pillars 7 a and 7 b in the first direction is typically rounded through the manufacturing process. Therefore, in this case, L2 is a longest line segment among point-to-point distances between intersections of outer peripheral lines of the TiN layers 15 a and 15 b and straight lines extending in the first direction in plan view. Subsequently, as illustrated in FIGS. 1KA and 1KB, a SiO₂ layer 28 is formed at outer peripheral portions around the side surfaces of the top portions of the Si pillars 7 a and 7 b. Subsequently, an N⁺ layer 29 a and a P⁺ layer 29 b are formed by, for example, selective epitaxial growth so as to cover the top portions of the Si pillars 7 a and 7 b, respectively. Subsequently, an N⁺ layer 30 a and a P⁺ layer 30 b are formed in the top portions of the Si pillars 7 a and 7 b, respectively, by thermal diffusion.

Next, as illustrated in FIGS. 1LA and 1LB, W layers 32 a and 32 b are formed on the N⁺ layer 29 a and the P⁺ layer 29 b, respectively. Subsequently, a SiO₂ layer 33 is formed so as to cover the entire surface. Subsequently, a contact hole C1 is formed in the SiO₂ layers 28 and 33 on the W layer 26. A contact hole C2 is formed in the SiO₂ layer 33 on the W layer 32 a. A contact hole C3 is formed in the SiO₂ layer 33 on the W layer 32 b. Subsequently, a contact hole C4 is formed in the SiO₂ layers 24, 28, and 33 on the W layer 22. Subsequently, an input wiring metal layer Vin connecting to the W layer 26 through the contact hole C1 is formed. Subsequently, a ground wiring metal layer Vss connecting to the W layer 32 a through the contact hole C2 is formed. Subsequently, a power supply wiring metal layer Vdd connecting to the W layer 32 b through the contact hole C3 is formed. Subsequently, an output wiring metal layer Vout connecting to the W layer 22 through the contact hole C4 is formed. Thus, an inverter circuit is formed on the P layer substrate 1 a.

In the description of this embodiment, the shape of the Si pillars 7 a and 7 b is rectangular in plan view. However, the shape in plan view may be rounded at both ends in the direction perpendicular to the line X-X′, circular, or elliptical.

In FIGS. 1FA and 1FB, the thickness of the TiN layer 15, which serves as a gate conductor layer, is larger than those of the SiN layers 17 a and 17 b. However, the thickness of the TiN layer 15 may be smaller than those of the SiN layers 17 a and 17 b, and a protective layer for the TiN layer 15 may be provided outside the TiN layer 15, the protective layer being composed of one or more conductor layers such as TaN layers or one or more insulating material layers such as SiN layers. In this case, in the process of forming the gate TiN layers 15 a and 15 b in FIGS. 1GA and 1GB, the protective layer is left so as to surround the side surfaces of the gate TiN layers 15 a and 15 b. When an insulating protective layer such as a SiN layer is formed, the insulating protective layer around the side surfaces of the top portions of the gate TiN layers 15 a and 15 b is removed before the formation of the W layer 26 in FIGS. 1JA and 1JB.

The N⁺ layer 30 a and the P⁺ layer 30 b formed in the top portions of the Si pillars 7 a and 7 b, respectively, may be, for example, an N⁺ layer and a P⁺ layer that are formed on the P layer 4 by epitaxial crystal growth after the formation of the P layer 4 in FIGS. 1BA and 1BB. In this case, the step, as illustrated in FIGS. 1KA and 1KB, of forming the N⁺ layer 30 a and the P⁺ layer 30 b by performing heat treatment to cause thermal diffusion of donor and acceptor impurities from the N⁺ layer 29 a and the P⁺ layer 29 b into the top portions of the Si pillars 7 a and 7 b, respectively, is not necessary. When the SiO₂ layer 28 is thick, if a high-temperature, long heat treatment is performed so that the lower ends of the N⁺ layer 30 a and the P⁺ layer 30 b become flush with the upper ends of the gate TiN layers 15 a and 15 b in the vertical direction, the gate TiN layers 15 a and 15 b and the HfO₂ layer 14 serving as a gate insulating layer may be damaged. To overcome this problem, the following procedure may be employed: a P⁺ layer and an N⁺ layer are formed on the P layer 4 after the formation of the P layer 4 and before the formation of the mask material layers 5 a and 5 b in FIGS. 1BA and 1BB, and from these P⁺ layer and N⁺ layer, the N⁺ layer 30 a and the P⁺ layer 30 b are formed in the top portions of the silicon pillars 7 a and 7 b. This can avoid thermal damage to the gate TiN layers 15 a and 15 b and the HfO₂ layer 14 serving as a gate insulating layer, as described above. This also eliminates the need for forming the N⁺ layer 30 a and the P⁺ layer 30 b in the top portions of the Si pillars 7 a and 7 b, respectively, by thermal diffusion at the stage of FIGS. 1KA and 1KB, thus facilitating the formation of impurity regions in the top portions of the Si pillars 7 a and 7 b. In this case, the N⁺ layer 29 a and the P⁺ layer 29 b may be, but need not be, formed. In this case, the N⁺ layer 29 a and the P⁺ layer 29 b may be replaced with conductor layers made of, for example, a metal or an alloy.

While the W layer 22 is formed directly on the N⁺ layer 3 aa and the P⁺ layer 3 bb, the W layer 22 may be formed after a conductor layer made of a metal or an alloy is formed on the upper surfaces of the N⁺ layer 3 aa and the P⁺ layer 3 bb between the Si pillars 7 a and 7 b. In addition, a conductor layer such as a TiN layer for reducing the contact resistance between the W layer 22 and the N⁺ layer 3 aa and between the W layer 22 and the P⁺ layer 3 bb may be formed below the W layer 22.

In the description of this embodiment, the Si pillar 7 a forming an N-channel SGT and the Si pillar 7 b forming a P-channel SGT have the same length in the direction perpendicular to the line X-X′ in plan view. However, the length of the Si pillar 7 a forming an N-channel SGT in the direction perpendicular to the line X-X′ in plan view may be smaller than that of the Si pillar 7 b forming a P-channel SGT. Alternatively, the Si pillar 7 a forming an N-channel SGT and the Si pillar 7 b forming a P-channel SGT may have different lengths in the line X-X′ direction in plan view.

This embodiment provides the following features.

-   -   1. In this embodiment, as illustrated in FIGS. 1HA, 1HB, 1IB,         and 1IB, after TiN layers 15 a and 15 b serving as gate         electrodes are formed, a contact hole 21 is formed, and a bottom         connecting wiring W layer 22 connecting to the N⁺ layer 3 aa and         the P⁺ layer 2 bb is then formed at a bottom portion of the         contact hole 21. Subsequently, a SiO₂ layer 24 effectively         serving as a low-dielectric-constant layer and having a hole 25         is formed in the contact hole 21 on the W layer 22. Thereafter,         as illustrated in FIGS. 1JA and 1JB, an input wiring W layer 26         connected to the gate electrode TiN layers 15 a and 15 b is         formed on the SiO₂ layers 20 a and 24 a so as to be orthogonal         to the bottom connecting wiring W layer 22 in plan view.

The above process offers the following features.

-   -   (1) Since the SiO₂ layer 24 a, which serves as a         low-dielectric-constant layer by virtue of the hole 25, and the         bottom connecting W layer 22 are formed in the contact hole 21,         the bottom connecting W layer 22 and the SiO₂ layer 24 a serving         as a low-dielectric-constant layer are formed in a self-aligned         manner. This can provide a circuit with higher integration. As         illustrated in FIGS. 1LA and 1LB, the SiO₂ layer 24 having the         hole 25 and effectively serving as a low-dielectric-constant         layer is present in a region where the bottom connecting W layer         22 and the input wiring W layer 26 overlap each other in plan         view. This can reduce the capacitance between the bottom         connecting W layer 22 and the input wiring W layer 26. This can         provide an SGT-including circuit with higher performance.     -   (2) The bottom connecting W layer 26 connected to the input         wiring metal layer Vin is connected only to upper portions of         the gate electrodes 15 a and 15 b in the height direction. This         configuration can significantly reduce the capacitance between         the input wiring metal layer Vin and the output wiring metal         layer Vout compared, for example, to a configuration in which         the bottom connecting W layer 26 a connected to the input wiring         metal layer Vin is formed so as to have the same height as those         of the gate electrodes 15 a and 15 b.     -   2. In this embodiment, as illustrated in FIGS. 1EA and 1EB, the         P layer base 12 is shaped such that portions surrounding the Si         pillars 7 a and 7 b protrude at outer portions of the N⁺ layer 3         aa and the P⁺ layer 3 bb in plan view. These protruding portions         are formed in a self-aligned manner with the Si pillars 7 a and         7 b. This self-alignment enables the protruding P layer base 12         to be formed as a small area with high accuracy. This can         provide an SGT-including circuit with higher integration.     -   3. In this embodiment, as illustrated in FIGS. 1FA, 1FB, 1GA,         and 1GB, the TiN layers 15 a and 15 b serving as gate electrodes         are formed in a self-aligned manner with respect to the Si         pillars 7 a and 7 b, respectively. As illustrated in FIGS. 1JA         and 1JB, the W layer 26 is formed in a band shape in the line         X-X′ direction so as to be connected to portions of the outer         peripheries of the gate electrode TiN layers 15 a and 15 b. In         plan view, the width of the W layer 26 in the direction         perpendicular to the line X-X′ is smaller than the length of         outer peripheral long sides of the TiN layers 15 a and 15 b.

The above process offers the following features.

-   -   (1) The W layer 26 is formed using the mask material layer 27 as         an etching mask separately from the formation of the gate line         TiN layers 15 a and 15 b. This enables the width of the W layer         26 a in the direction perpendicular to the line X-X′ to be as         small as possible while satisfying the condition that the W         layer 26 connect to the gate line TiN layers 15 a and 15 b. This         can further reduce the capacitance between the W layer 26 and         the bottom connecting W layer 22. The gate TiN layers 15 a and         15 b are formed in a self-aligned manner with respect to the Si         pillars 7 a and 7 b, respectively. This can provide an         SGT-including circuit with even higher integration.

Second Embodiment

Hereinafter, a method for manufacturing an inverter circuit according to a second embodiment of the present invention will be described with reference to FIGS. 2A and 2B. FIG. 2A is a plan view, and FIG. 2B is a sectional structural view taken along line X-X′ in FIG. 2A. In the first embodiment, the Si pillar 7 a forming an N-channel SGT and the Si pillar 7 b forming a P-channel SGT are formed side by side in the line X-X′ direction with the bottom connecting wiring W layer 22 interposed therebetween. In this embodiment, two Si pillars, an N-channel SGT and a P-channel SGT, are disposed in the direction perpendicular to the line X-X′ direction, and a W layer extending in the direction perpendicular to the line X-X′ direction adjacently to the two Si pillars in plan view and corresponding to the bottom connecting wiring W layer 22 is formed. In this embodiment, a method for manufacturing an inverter circuit including two N-channel SGTs connected to each other in parallel and two P-channel SGTs connected to each other in parallel is described. This manufacturing method is basically the same as that in the first embodiment.

As illustrated in FIGS. 2A and 2B, Si pillars 7A, 7B, 7C, and 7D, which are rectangular in plan view, are formed on a P layer substrate 1A. Subsequently, a semiconductor base 12 a constituted by an upper portion of the P layer substrate 1A, an N layer 2A, a P⁺ layer 3A, and an N⁺ layer 3B is formed on the P layer substrate 1A. In plan view, the P⁺ layer 3A underlies the Si pillars 7A and 7B, and the N⁺ layer 3B underlies the Si pillars 7C and 7D. Subsequently, a SiO₂ layer 13A is formed such that the upper surface thereof is flush with the upper surfaces of the P⁺ layer 3A and the N⁺ layer 3B. Subsequently, a gate insulating layer 14 a is formed so as to surround the Si pillars 7A to 7D. Subsequently, gate TiN layers 15A, 15B, 15C, and 15D are formed so as to surround the gate insulating layers 14 a on the side surfaces of the Si pillars 7A, 7B, 7C, and 7D, respectively. Subsequently, a SiO₂ layer 20A whose upper surface is located below the upper ends of the gate TiN layers 15A, 15B, 15C, and 15D is formed so as to surround the gate TiN layers 15A, 15B, 15C, and 15D. Subsequently, contact holes (not illustrated) extending in a band shape in a direction perpendicular to line X-X′ are formed on the P⁺ layer 3A and the N⁺ layer 3B on both sides of the gate TiN layers 15B and 15D in plan view. Subsequently, bottom connecting wiring W layers 22 a and 22 b connected to the P⁺ layer 3A and the N⁺ layer 3B are formed at bottom portions of the contact holes. The bottom connecting wiring W layer 22 a is formed between the gate TiN layers 15A and 15C and the gate TiN layers 15B and 15D in plan view.

Subsequently, as illustrated in FIGS. 2A and 2B, SiO₂ layers 24 a and 24 b which have holes 25 a and 25 b, respectively, and whose upper surfaces are located below the upper end surfaces of the gate TiN layers 15A to 15D are formed so as to fill the contact holes on the bottom connecting wiring W layers 22 a and 22 b, respectively. Subsequently, a wiring conductor W layer 26 a connecting to the gate TiN layers 15A and 15B and extending in the line X-X′ direction, a wiring conductor W layer 26 b connecting to the gate TiN layers 15A and 15C and extending in the direction perpendicular to line X-X′, and a wiring conductor W layer 26 c connecting to the gate TiN layers 15B and 15D and extending in the direction perpendicular to line X-X′ are formed. Subsequently, top portions of the Si pillars 7A to 7D are exposed, and a SiN layer 28 a is formed at outer peripheral portions of the exposed top portions. Subsequently, for example, by selective epitaxial growth, P⁺ layers 29A and 29B are formed so as to cover the top portions of the Si pillars 7A and 7B, respectively, and N⁺ layers 29C (not illustrated) and 29D (not illustrated) are formed so as to cover the top portions of the Si pillars 7C and 7D, respectively. Subsequently, P⁺ layers 30A and 30B and N⁺ layers 30C (not illustrated) and 30D (not illustrated) are formed on the top portions of the Si pillars 7A, 7B, 7C, and 7D, respectively, by thermal diffusion. Subsequently, W layers 32A, 32B, 32C (not illustrated), and 32D (not illustrated) are formed on the P⁺ layers 29A and 29B and the N⁺ layers 29C and 29D, respectively. Subsequently, an input wiring metal layer Vin connecting to the W layer 26 a through a contact hole C4 is formed. Subsequently, a power supply wiring metal layer Vdd connecting to the W layers 32A and 32B respectively through contact holes C5 a and C5 b is formed. Subsequently, an output wiring metal layer Vout connecting to the W layers 22 a and 22 b respectively through contact holes C6 a and C6 b is formed. Subsequently, a ground wiring metal layer Vss connecting to the W layers 32C and 32D respectively through contact holes C7 a and C7 b is formed. Thus, an inverter circuit including two P-channel SGTs connected to each other in parallel and two N-channel SGTs connected to each other in parallel on the P layer substrate 1A is formed.

As described above, an inverter circuit including P-channel SGTs connected to each other in parallel and N-channel SGTs connected to each other in parallel can achieve a higher drive current due to the increase in the number of P-channel SGTs and N-channel SGTs connected in parallel.

The gate TiN layers 15A to 15D are electrically connected through the W layers 26 a to 26 c. Due to this configuration, the W layer 26 a connecting to the input wiring metal layer Vin may be provided anywhere in the direction perpendicular to the line X-X′ direction in plan view as long as the W layer 26 a is connected to the gate TiN layers 15A and 15B or the gate TiN layers 15C and 15D.

In the description of this embodiment, the P⁺ layer 3A and the N⁺ layer 3B are continuously formed in plan view in the semiconductor base 12 a. Alternatively, the semiconductor base 12 a may be formed as two separate semiconductor bases, a first semiconductor base including the P⁺ layer 3A and a second semiconductor base including the N⁺ layer 3B. In this case, the W layers 22 a and 22 b are formed so as to be connected to the P⁺ layer 3A and the N⁺ layer 3B and to be continuous over the upper surface of the SiO₂ layer 13A disposed between the two semiconductor bases.

When the line resistance of the W layer 26 a needs to be small for the sake of circuit performance, the SiO₂ layer 33 a on the W layer 26 a may be provided with a plurality of contact holes, and a wiring metal layer connected to the input wiring metal layer Vin through the contact holes may be formed.

This embodiment provides the following features.

-   -   1. As in the first embodiment, the W layers 22 a and 22 b formed         on the semiconductor base, and the W layer 26 a orthogonal to         and overlapping the W layers 22 a and 22 b in plan view are         formed so as to be separate from each other in the vertical         direction. This can reduce the capacitance between the input         wiring metal layer Vin and the output wiring metal layer Vout.         Furthermore, as in the first embodiment, the SiO₂ layers 24 a         and 24 b having the holes 25 a and 25 b, respectively, and         effectively serving as low-dielectric material layers are formed         in a self-aligned manner on the W layers 22 a and 22 b,         respectively. This can further reduce the capacitance between         the input wiring metal layer Vin and the output wiring metal         layer Vout.     -   2. In this embodiment, the Si pillar 7A, which is a P-channel         SGT, and the Si pillar 7C, which is an N-channel SGT, are         aligned in the direction perpendicular to the line X-X′         direction to form a first inverter circuit. Likewise, the Si         pillar 7B, which is a P-channel SGT, and the Si pillar 7D, which         is an N-channel SGT, are aligned in the direction perpendicular         to the line X-X′ direction to form a second inverter circuit.         For example, when an inverter-ring oscillator circuit is formed         using these two inverter circuits, the coupling capacitance         between input electrodes of the first inverter circuit (in this         case, the gate TiN layers 15A and 15C) and input electrodes of         the second inverter circuit (in this case, the gate TiN layers         15B and 15D) is a problem. However, by disposing the SiO₂ layer         24 a effectively serving as a low-dielectric material layer         between the gate TiN layers 15A and 15C and the gate TiN layers         15B and 15D as in this embodiment, the coupling capacitance can         be reduced.

Third Embodiment

Hereinafter, a method for manufacturing an inverter circuit according to a third embodiment of the present invention will be described with reference to FIGS. 3A and 3B. FIG. 3A is a plan view, and FIG. 3B is a sectional structural view taken along line X-X′ in FIG. 3A.

In the second embodiment, as illustrated in FIGS. 2A and 2B, the input wiring metal layer Vin connects through the contact hole C4 to the W layer 26 a connected to long sides of the gate TiN layers 15A and 15B perpendicular to line X-X′ in plan view. By contrast in this embodiment, as illustrated in FIGS. 3A and 3B, contact holes C4 a and C4 b are respectively formed on a W layer 26 b which connects gate TiN layers 15A and 15C aligning in the direction perpendicular to line X-X′ in plan view and a W layer 26 c which connects gate TiN layers 15B and 15D. An input wiring metal layer VIN is connected to the W layers 26 b and 26 c respectively through the contact holes C4 a and C4 b. Thus, an inverter circuit including two P-channel SGTs connected to each other in parallel and two N-channel SGTs connected to each other in parallel on a P layer substrate 1A is formed. Except for the above, this inverter circuit is formed by the same process as illustrated in FIGS. 2A and 2B.

This embodiment provides the following features.

In the second embodiment, at portions where the W layer 26 a overlaps the W layers 22 a and 22 b in plan view, the SiO₂ layers 24 a and 24 b having the holes 25 a and 25 b, respectively, are present between the W layer 26 a and the W layers 22 a and 22 b. By contrast in the third embodiment, the input wiring metal layer VIN overlaps the W layers 22 a and 22 b in plan view. At these overlapping portions, the SiO₂ layers 24 a and 24 b having the holes 25 a and 25 b, respectively, and the SiO₂ layers 28 a and 33 a are present between the input wiring metal layer VIN and the W layers 22 a and 22 b. Due to this configuration, the capacitance between the input wiring metal layer VIN and the output wiring metal layer Vout can be reduced in the third embodiment.

OTHER EMBODIMENTS

For example, the first embodiment has the feature that the W layer 22 connecting to the N⁺ layer 3 aa serving as a source or a drain at the bottom of one SGT formed at the Si pillar 7 a and the W layer 26 connecting to the gate TiN layer 15 a overlap each other in plan view with the SiO₂ layer 24, which is an effective low-dielectric-constant layer, interposed therebetween. Similarly, the third embodiment has the feature that the W layers 22 a and 22 b connecting to the P⁺ layer 3A and the W layer 26 a connecting to the gate TiN layers 15A and 15B overlap each other in plan view with the SiO₂ layers 24 a and 24 b, which are effective low-dielectric-constant layers, and the holes 25 a and 25 b interposed therebetween. The present invention is also applicable to logic circuits including other SGTs, selector elements such as a dynamic random access memory (DRAM), a phase change memory (PCM), a magnetic random access memory (MRAM), and a resistive random access memory (RRAM), and other circuits such as peripheral circuits as long as it has any of the above features. The same applies to the second embodiment.

While the Si pillars 7 a and 7 b are formed in the first embodiment, semiconductor pillars made of other semiconductor materials may also be used. The same applies to other embodiments according to the present invention.

The N⁺ layer 3 aa and the P⁺ layer 3 bb in the first embodiment may each be formed of Si containing a donor impurity or an acceptor impurity or any other semiconductor material. The N⁺ layers 3 aa and 29 a and the P⁺ layers 3 bb and 29 b may be formed of different semiconductor materials. The same applies to other embodiments according to the present invention.

In the description of the first embodiment, it has been mentioned that the N⁺ layer 30 a and the P⁺ layer 30 b formed in the top portions of the Si pillars 7 a and 7 b, respectively, may be, for example, an N⁺ layer and a P⁺ layer that are formed on the P layer 4 by epitaxial crystal growth after the formation of the P layer 4 in FIGS. 1BA and 1BB. These N⁺ layer and P⁺ layer may be formed by another method different from epitaxial crystal growth. The same applies to other embodiments according to the present invention.

Since the first embodiment has been described in the context of an inverter circuit, the P⁺ layers 29 b and 30 b and the N⁺ layers 29 a and 30 a serve as sources, and the P⁺ layer 3 bb and the N⁺ layer 3 aa operate as drains, but depending on the circuit to be manufactured, impurity layers at upper and lower portions of SGTs can each serve as a source or a drain. The same applies to other embodiments according to the present invention.

The mask material layers 5 a, 5 b, 11, and 27 used in the first embodiment may be replaced with another material layer having a single-layer structure or a multilayer structure and containing an organic material or an inorganic material as long as the material is suitable for the object of the present invention. The SiO₂ layer 9 a and the SiN layers 10 a and 10 b used as etching masks may also be replaced with another material layer having a single-layer structure or a multilayer structure and containing an organic material or an inorganic material as long as the material is suitable for the object of the present invention. The same applies to other embodiments according to the present invention.

The W layer 22 in the first embodiment may be made of not only a metal but also a conductive material such as an alloy, an alloy containing an acceptor or donor impurity in a large amount, or a semiconductor and may have a single-layer structure or a multilayer structure. The same applies to other embodiments according to the present invention.

In the first embodiment, the TiN layers 15 a and 15 b are used as gate conductor layers. The TiN layers 15 a and 15 b may each be any material layer having a single-layer structure or a multilayer structure as long as the material is suitable for the object of the present invention. The TiN layers 15 a and 15 b may each be formed of a conductor layer having at least a desired work function, such as a metal layer having a single-layer structure or a multilayer structure. Another conductive layer such as a W layer may be formed outside the TiN layers. Instead of the W layer, a metal layer having a single-layer structure or a multilayer structure may be used.

The W layer 26 connecting to the TiN layers 15 a and 15 b in the first embodiment may be formed of a laminate with another conductor layer or formed of another conductor layer. The same applies to other embodiments according to the present invention.

Furthermore, while the HfO₂ layer 14 is used as a gate insulating layer, other material layers each having a single-layer structure or a multilayer structure may be used. The same applies to other embodiments according to the present invention.

In FIGS. 1HA and 1HB and FIGS. 1IA and 1IB of the first embodiment, the SiO₂ layer 24 having the hole 25 is formed. However, an upper portion of the contact hole 21 may be covered with a SiN layer by, for example, chemical vapor deposition (CVD) to form the hole 25. Alternatively, an insulating layer formed of an inorganic or organic layer having the hole 25 may be formed by another method.

In the first embodiment, the shapes of the Si pillars 7 a and 7 b in plan view are rectangular. The shapes of these Si pillars in plan view may not only be rectangular but also be circular, elliptical, or U-shaped. These shapes may coexist on the same P layer substrate 1 a. The same applies to other embodiments according to the present invention.

While the first embodiment has been described in the context of an inverter circuit including one N-channel SGT and one P-channel SGT, a plurality of N-channel SGTs and P-channel SGTs may be connected in parallel in order to achieve a high drive current or low effective SGT series resistance. The same applies to other embodiments according to the present invention.

This embodiment has been described in the context of an inverter circuit. In addition to this, the present invention is also applicable to an SGT-including circuit in which a conductor layer (the W layer 22 in the first embodiment) that is connected to an impurity region (the N⁺ layer 3 aa or the P⁺ layer 3 bb in the first embodiment) formed at a bottom portion of an SGT and serving as a source or a drain and that extends in a band shape in the first direction and a wiring conductor layer (the W layer 26 in the first embodiment) that connects to a gate conductor layer (the TiN layer 15 a or the TiN layer 15 b in the first embodiment) and that is perpendicular to the first direction are formed so as to overlap each other in plan view.

While one SGT is formed at one semiconductor pillar in the embodiments according to the present invention, the present invention is also applicable to the formation of circuits in which two or more SGTs are formed at one semiconductor pillar.

While the SGTs are formed on the P layer substrate 1 in the first embodiment, the P layer substrate 1 may be replaced with a silicon-on-insulator (SOI) substrate. Alternatively, any other material substrate may be used as long as it serves as a substrate. The same applies to other embodiments according to the present invention.

While the first embodiment has been described in the context of SGTs in which sources and drains are formed on the upper and lower sides of the Si pillars 7 a and 7 b using the N⁺ layers 3 aa, 29 a, and 30 a and the P⁺ layers 3 bb, 29 b, and 30 b having conductivity of the same polarity, the present invention is also applicable to tunneling SGTs including sources and drains having different polarities. The same applies to other embodiments according to the present invention.

Various embodiments and modifications of the present invention can be made without departing from the broad spirit and scope of the present invention. The foregoing embodiments are illustrative of examples of the present invention and are not intended to limit the scope of the present invention. The foregoing examples and modifications can be combined in any manner. Furthermore, the foregoing embodiments fall within the scope of the technical idea of the present invention even if some elements are excluded from those embodiments as needed.

The method for manufacturing a pillar-shaped semiconductor device according to the present invention provides a pillar-shaped semiconductor device with high density and high performance. 

What is claimed is:
 1. A method for manufacturing a pillar-shaped semiconductor device that includes a first semiconductor pillar standing in a direction perpendicular to a substrate, a first impurity region disposed at a bottom portion of the first semiconductor pillar, a second impurity region disposed at a top portion of the first semiconductor pillar, one of the first impurity region and the second impurity region serving as a source, the other serving as a drain, the first semiconductor pillar between the first impurity region and the second impurity region serving as a channel, a first gate insulating layer surrounding the first semiconductor pillar disposed between the first impurity region and the second impurity region, and a first gate conductor layer surrounding the first gate insulating layer, the method comprising: a step of forming the first impurity region such that the first impurity region extends in a band shape in a first direction in plan view; a step of forming the first semiconductor pillar that overlaps the first impurity region in plan view; a step of forming a semiconductor base that includes the first semiconductor pillar and the first impurity region and extends in a band shape in the first direction in plan view such that the semiconductor base connects to the bottom portion of the first semiconductor pillar; a step of forming the first gate insulating layer and the first gate conductor layer such that the first semiconductor pillar is surrounded; a step of forming a first insulating layer at an outer peripheral portion of the first gate conductor layer; a step of forming, in the first insulating layer, a contact hole that overlaps the first impurity region disposed in the semiconductor base in plan view, has a bottom portion in contact with the first impurity region, and extends in a band shape in the first direction; a step of forming, at the bottom portion of the contact hole, a first conductor layer that is in contact with the first impurity region and extends in a band shape in the first direction; a step of forming, in the contact hole on the first conductor layer, a second insulating layer that has a hole or is made of a low-dielectric-constant material; a step of lowering an upper surface of the second insulating layer below an upper end of the first gate conductor layer; and a step of forming a second conductor layer that is in contact with the first gate conductor layer and extends in a band shape in a second direction perpendicular to the first direction in plan view.
 2. The method for manufacturing a pillar-shaped semiconductor device according to claim 1, further comprising: a step of forming the first semiconductor pillar using a first mask material layer as an etching mask; a step of forming a third insulating layer that surrounds the first semiconductor pillar and has an upper surface located at a bottom portion of the first mask material layer or the top portion of the first semiconductor pillar in the direction perpendicular to the substrate; a step of forming a second mask material layer that is disposed on the third insulating layer and surrounds the exposed first mask material layer and the top portion of the first semiconductor pillar with an equal width in plan view; a step of forming, on the third insulating layer, a third mask material layer that partially overlaps the second mask material layer and extends in a band shape in the first direction in plan view; and a step of forming the semiconductor base by etching the third insulating layer and the first impurity layer using the first mask material layer, the second mask material layer, and the third mask material layer as masks.
 3. The method for manufacturing a pillar-shaped semiconductor device according to claim 1, wherein, in the first direction in plan view, the second conductor layer is formed so as to have a width that is smaller than a longest line segment among point-to-point distances between intersections of an outer peripheral line of the first gate conductor layer and straight lines extending in the first direction.
 4. The method for manufacturing a pillar-shaped semiconductor device according to claim 1, wherein, in the direction perpendicular to the substrate, the first conductor layer is formed so as to have an upper end that is located below a lower end of the first gate conductor layer.
 5. The method for manufacturing a pillar-shaped semiconductor device according to claim 1, wherein, in the direction perpendicular to the substrate, the hole is formed so as to have an upper end that is located below an upper end of the first gate conductor layer.
 6. The method for manufacturing a pillar-shaped semiconductor device according to claim 1, further comprising: a step of forming a second semiconductor pillar on the semiconductor base on an opposite side of the first conductor layer from the first semiconductor pillar in the second direction in plan view; a step of forming a second gate insulating layer such that the second gate insulating layer surrounds the second semiconductor pillar; a step of forming a second gate conductor layer such that the second gate conductor layer surrounds the second gate insulating layer; and a step of forming the second conductor layer that extends in the second direction in plan view and is connected to an upper end portion of the second gate conductor layer.
 7. The method for manufacturing a pillar-shaped semiconductor device according to claim 1, further comprising: a step of forming a third impurity region that is disposed in the semiconductor base and is adjacent to the first impurity region in the first direction in plan view; a step of forming a third semiconductor pillar on the third impurity region; a step of forming a third gate insulating layer such that the third gate insulating layer surrounds the third semiconductor pillar; a step of forming a third gate conductor layer such that the third gate conductor layer surrounds the third gate insulating layer; a step of forming the second conductor layer such that the second conductor layer extends in the first direction and is in contact with the third impurity region in plan view; and a step of forming a third conductor layer that extends in the second direction in plan view and connects to upper portions of the first gate conductor layer and the third gate conductor layer.
 8. The method for manufacturing a pillar-shaped semiconductor device according to claim 1, further comprising: a step of forming, on the substrate, a first impurity layer on which the first impurity region is based; a step of forming, on the first impurity layer, a first semiconductor layer on which the first semiconductor pillar is partially based; and a step of forming, on the first semiconductor layer, a second impurity layer on which the first semiconductor pillar is partially based and which forms at least a part of the second impurity region.
 9. The method for manufacturing a pillar-shaped semiconductor device according to claim 8, further comprising: a step of forming, on the second impurity region, a third impurity layer having the same polarity as that of the second impurity region or a conductive layer made of an alloy or a metal.
 10. A pillar-shaped semiconductor device comprising: a first semiconductor pillar standing perpendicularly with respect to a substrate; a first impurity region connecting to a bottom portion of the first semiconductor pillar and extending in a band shape in a first direction; a second impurity region disposed at a top portion of the first semiconductor pillar; a first gate insulating layer surrounding the first semiconductor pillar disposed between the first impurity region and the second impurity region; a first gate conductor layer surrounding the first gate insulating layer; a semiconductor base connecting to the bottom portion of the first semiconductor pillar, including the first impurity region, and extending in a band shape in the first direction in plan view; a first insulating layer disposed at an outer peripheral portion of the first gate conductor layer; a first material layer disposed in the first insulating layer, overlapping the first impurity region disposed in the semiconductor base in plan view, having a bottom portion in contact with the first impurity region, and extending in a band shape in the first direction and also extending in a vertical direction; a first conductor layer extending in a band shape in the first direction so as to be in contact with the first impurity region at a bottom portion of the first material layer; a second insulating layer in which the first material layer on the first conductor layer has a hole whose upper surface is located below an upper end of the first gate conductor layer or which is made of a low-dielectric-constant material; and a second conductor layer connecting to the first gate conductor layer and extending in a band shape in a second direction perpendicular to the first direction in plan view, wherein the first conductor layer and the second conductor layer overlap each other at an intersection in plan view.
 11. The pillar-shaped semiconductor device according to claim 10, wherein the second conductor layer connects to the first gate conductor layer in a contact manner, and in the first direction in plan view, the second conductor layer is formed so as to have a width that is smaller than a longest line segment among point-to-point distances between intersections of an outer peripheral line of the first gate conductor layer and straight lines extending in the first direction.
 12. The pillar-shaped semiconductor device according to claim 10, wherein, in a direction perpendicular to the substrate, an upper end of the first conductor layer is located below a lower end of the first gate conductor layer.
 13. The pillar-shaped semiconductor device according to claim 10, comprising: a second semiconductor pillar disposed on the semiconductor base on an opposite side of the first conductor layer from the first semiconductor pillar in the second direction in plan view; a second gate insulating layer surrounding the second semiconductor pillar; a second gate conductor layer surrounding the second gate insulating layer; and the second conductor layer extending in the second direction in plan view and connected to an upper end portion of the second gate conductor layer.
 14. The pillar-shaped semiconductor device according to claim 10, comprising: a third impurity region disposed in the semiconductor base and adjacent to the first impurity region in the first direction in plan view; a third semiconductor pillar disposed on the third impurity region; a third gate insulating layer surrounding the third semiconductor pillar; and a third gate conductor layer surrounding the third gate insulating layer, wherein the first conductor layer extends in the first direction and is adjacent to the third semiconductor pillar in plan view, the pillar-shaped semiconductor device further comprising a third conductor layer extending in the second direction in plan view and connecting to upper portions of the first gate conductor layer and the third gate conductor layer.
 15. The pillar-shaped semiconductor device according to claim 14, further comprising: a second insulating layer on the third conductor layer; a first contact hole disposed in the second insulating layer on the third conductor layer; and the second conductor layer disposed on the second insulating layer and connecting to the third conductor layer through the first contact hole.
 16. The pillar-shaped semiconductor device according to claim 10, further comprising, on the second impurity region, a third impurity layer having the same polarity as that of the second impurity region or a conductive layer made of an alloy or a metal. 